Inkjet printers have been proposed wherein an inkjet printer can be used to print on various recording media differing in thickness and size. In Patent Document 1, the present applicants have proposed a large-sized inkjet printer suitable for printing on the surfaces of wooden plates, round wooden objects, and other such thick recording media. This large-sized printer is configured so that printing is performed by conveying a medium-conveying tray carrying a recording medium through the printing position of the print head. The printer is also configured so that the gap between the print head and the recording medium is adjusted by raising and lowering the conveying mechanism of the medium-conveying tray. [Patent Document 1] JP-A 2000-190467
In the inkjet printer, ink droplets discharged from the inkjet head are deposited on the surface of the recording medium. The droplets harden as they are absorbed, and the droplets become fixed on the surface. The recording medium surface can be heated in order to efficiently fix the deposited ink droplets. Heating is particularly effective in cases in which printing is performed on a recording medium composed of a material on which aqueous ink, solvent ink, or the like does not readily fix. In cases in which printing is performed using a thermosetting ink such as resin ink or the like, heating is essential because the ink droplets deposited on the recording medium must be heated and hardened.
In a common heating method, a platen regulating the printing position of the inkjet head is heated, and the portion of the recording medium where the ink droplets are deposited is also heated. However, although this heating method is effective with a thin recording medium such as paper, this method is not effective in the case of a thick recording medium because a long time is required in order to heat the recording medium to a temperature suitable for hardening the ink.
The inkjet head is disposed facing the platen across a small gap, and printing is performed while the inkjet head moves along the platen. Accordingly, with a method for heating the platen, the inkjet head facing the platen is also heated, and the ink in the ink nozzles thickens and coagulates, causing ink clogging. Depending on the situation, there is a possibility that the inkjet head will be thermally damaged.
Furthermore, it is difficult to keep the portion of the recording medium passing over the platen in a state of uniform heating. Therefore, nonuniformity occurs in the printing quality, and the printing quality may be compromised.
In addition, nichrome wire or the like has been used as the heating means in the past, but conventional heating means must be constantly energized, and problems with large power consumption and high running costs are encountered.